Yep, pin-1 & pin-2 are the input power, I normally wire 18V AC track power to them.
There's not a bridge, it's a single diode. The half-wave is for a specific reason, TMCC is a common ground reference for all the signals, so I couldn't have a bridge rectifier or I'd have had to arrange isolation for all the signals! That being the case, the signals coming into the Super-Chuffer II will all be referenced to pin-2 as their common.
There is no problem putting anything up to track voltage on pin-9. Pin-9 and pin-3 (Headlight in) have input circuitry designed to handle up to full track voltage.
